Occurrence of free D-aspartate and aspartate racemase in the blood shell Scapharca broughtonii

Substantial concentrations of D-aspartate were found in several tissues of Scapharca broughtonii together with approximately equal concentrations of L-aspartate. The foot and mantle extracts also contained an aspartate racemase activity. The formation of L-aspartate from the D-enantiomer by the foot extract was apparently slower than the reverse reaction, and this unbalance seemed to be due to the presence of an enzyme activity which rapidly converted L-aspartate to L-alanine. The possible role of D-aspartate in the anaerobiosis was discussed.